making faces of a sword smooth with
Turn on smooth shading and then use autosmooth so the smooth shading doesn't effect the sharp edges.

To enable smooth shading: in the pannel of the left, which you bring up by pressing T, click on the smooth option under shading. 

To enable autosmooth: In the section on the right with render settings and material click on the tab with a icon of 3 vertices connected.  

Tick the autosmooth option.